[ The highest wind states are getting to be enormously dependent on natural gas to balance wind and solar as this EIA article about California below shows. Yet conventional natural gas has peaked — half our natural gas– and is declining at 5% a year. Shale “fracked” natural gas is expected to peak by 2020, and can decline by 80% within a few years, and is already $400 billion in debt. Natural gas is not only balancing wind and solar, but it also provides base load power (running most of the time for 24 hours), and medium load (from 7 am to 6 pm on week days). On top of that, natural gas has been replacing coal and nuclear plants, and expected to do so even more in the future. Add in a growing population and natural gas will be declining at a much faster rate in the future than it has already. LNG import facilities aren’t a solution either. They take years to build and cost many billions of dollars, are fought tooth and nail by the ports where they’ll be put (the public sees them as an explosive bomb), and make us even more dependent on foreign nations.

Yet the LCOE costs of wind and solar look “cheap” because they don’t include Natural Gas LCOE, yet they rely nearly 100% on natural gas (to a smaller extent balancing can be done with biomass and (pumped) hydropower, but hydroelectric isn’t considered dispatchable because it’s seasonal and held back for agriculture, drinking water, and ecological needs.

Limits to natural gas mean limits to wind and solar penetration as well, since utility-scale battery storage and compressed air energy storage are far from commercial.

The California Independent System Operator (CAISO), the entity responsible for maintaining the balance between supply and demand for electricity throughout most of the state, where demand peaks in the late afternoon or early evening on summer days. Because of differences in the hourly output of certain electricity generators, some of which are nearly constant (nuclear) and some of which can vary considerably during the day (solar, wind), output from mainly natural gas and electricity imports from other regions are used to balance overall electricity supply and demand in the region.

Thermal generation in CAISO, mostly comes from natural gas, contributes the largest share of electricity generation in CAISO and has the widest range in hourly generation. Based on hourly data in June, July, and August, on the average summer day in 2016, in-region thermal power output ranged between 7.3 gigawatts and 15.2 gigawatts (GW). Over the entire summer, hourly thermal power output was as high as 25.6 GW at 5:00 p.m. on July 27, when total system demand was high, and was as low as 2.6 GW at 9:00 a.m. on June 12, an hour when demand was relatively low and renewables output was relatively high.

The only nuclear facility in CAISO, Diablo Canyon, consistently provided about 2.2 GW of power. Large hydroelectric facilities combined for about 2.3 GW to 4.8 GW of power on a typical day. Hydroelectric facilities, the most flexible renewable sources, were generally dispatched to coincide with electricity demand, meaning output was often highest during hours of peak electricity demand and lowest during times of low electricity demand.

Some renewable fuels have more variable levels of output, particularly wind and solar. Most of CAISO’s utility-scale solar generation comes from solar photovoltaic systems, whose output is dependent on sunlight during daylight hours. The CAISO area includes a few solar thermal facilities, some of which have energy storage that allows them to produce electricity after the sun has gone down, but these generators make up a relatively small portion of CAISO’s solar output. On an average summer day, utility-scale solar output ranged from 0 GW to 7.6 GW, the largest range among renewable fuels and the only fuel to have many hours without any output.

Wind generators provided about 2.2 GW on average, but they ranged from near zero (0.06 GW) to more than 4 GW several times during the summer. Wind output is often at its lowest point during the middle of the day, when solar output is near its highest. Geothermal, biomass, biogas, and small hydroelectric facilities had lower but more consistent output with relatively small differences between their highest and lowest hourly output.

Electricity imports are another option to supplement electricity produced by in-region sources to balance total supply with system load. Data from EIA’s new electric system operating tool show electricity trades among different balancing authorities. CAISO imports electricity from nearby regions such as the Northwest and Southwest. On an average summer day, these imports range between 6.5 GW and 9.4 GW.